New digital telephone terminals are now available with superior voice quality to that available as standard on conventional telephones. This voice quality is obtained by implementing a module for coding speech in the form of a broadband stream. These terminals therefore support several codecs so as to be able to establish a communication with any terminal whatsoever from the pool of existing terminals, in particular with the terminals having only a standard quality codec.
This type of coding, termed “broadband coding”, can be performed in accordance with the G.722 coding norm for a VoIP (Voice Over IP) terminal, while the coding termed “standard coding” may be in accordance with the G.711 coding norm. In the case of a communication established across a GSM mobile network, broadband communications are possible by means of an AMR WB codec. Conversion gateways are designed to transform a stream coded according to the G.722 standard into a stream coded according to the AMR WB standard and vice versa, so as to allow the establishment of broadband communications between a VoIP client terminal equipped with a G.722 codec and a mobile client terminal equipped with an AMR WB codec.
Indeed, to benefit from a telephonic communication of superior quality, it is necessary for both the calling terminal and the called terminal to have a broadband coding module, otherwise a communication between these terminals may be established only at standard quality.
Consequently, when establishing a communication from a first terminal equipped with a broadband codec, only a second terminal equipped with a broadband codec will be able to establish a communication at broadband quality with this first terminal.